The present subject relates to high quality doped transparent conducting oxide thin films. ZnO is a known transparent conducting oxide (TCO) material that is an important material in flat-panel displays and photovoltaic systems due to its high conductivity and transmission combined with relatively low cost. Zinc oxide is also very important due to the fact that it does not contain (scarce) indium or toxic cadmium and is amenable to scalable low-temperature deposition processes.
For example, U.S. Pat. No. 6,787,253 disclose a transparent electroconductive film having a polymer film and a transparent electroconductive layer deposited on the polymer film, wherein the electroconductive layer is resistant fully to delamination or removal and the electroconductive film has good electrical characteristics and good durability, and touch panels may be provided with the transparent electroconductive film. With reference to the transparent electroconductive layer deposited on the polymer film, transparent conductive oxide layer made of ITO (indium tin oxide), ATO (antimony tin oxide). ZnO, ZnO doped with Al, SnO2 may be used.
U.S. Pat. No. 6,685,623 discloses a method for manufacturing a zinc oxide semiconductor comprising the steps of forming a zinc oxide thin film including a Group 5 element as a dopant on a substrate by using a zinc oxide compound containing a Group 5 element or an oxide thereof, charging the substrate having the zinc oxide thin film formed thereon into a chamber for thermal annealing, and thermal annealing the substrate in the chamber to activate the dopant, thereby changing the zinc oxide thin film exhibiting n-type electrical properties or insulator properties to a zinc oxide thin film exhibiting p-type electrical properties. Since a zinc oxide thin film exhibiting n-type electrical properties can be changed to a zinc oxide thin film exhibiting p-type electrical properties, the provision of holes required for optical devices is facilitated, thereby enabling the development of photoelectric devices such as light-emitting diodes, laser diodes and UV sensors and further extending applicability of the zinc oxide semiconductor.
U.S. Pat. No. 6,569,548 disclose a transparent conductive film of zinc oxide, comprising a zinc oxide layer, and dopants doped into the zinc oxide layer, wherein the dopants have an n-type dopant and a p-type dopant, and the n-type dopant is more than the p-type dopant and doped into the zinc oxide layer in an impurity density of 1×1018 cm−3 or more. The transparent conductive film is at least one kind of element selected from the group consisting of elements of Group IIIB and elements of Group 5B, and the p-type dopant is at least one kind of element selected from the group consisting of elements of Group 5B and elements of Group 1A.
T. Miyata et al., Thin Solid Films, Vol. 411, pp. 76-81, 2002, disclose Fabrication of ZnO films with a Group 5B element as dopant but using d.c. magnetron sputtering, loose calcined power targets, and pure-argon sputtering ambient. Miyata et al. reports that their minimum resistivity (i.e., 5.3×10−4 Ohm-cm) is achieved at a mobility and carrier density of ˜35 cm2/V-sec and 3×1020 cm−3, respectively. Miyata reports that higher mobility is achieved only for lower carrier density.
There is a need in the area of transparent conducting oxide materials to have materials with an electron mobility significantly higher than that of the present state of the art, and yet simultaneously maintain high carrier density, and as good or better resistance to chemical corrosion than present state of the art transparent conducting oxide materials.
There is further a need to have TCO materials that are less sensitive to variation in oxygen content of the sputtering ambient because this can lead to non-uniformity in the electrical and optical properties of the film when deposited in large-area industrial applications.
The foregoing examples of the related art and limitations related therewith are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.